Identical PFGE Patterns Research Articles

Molecular, antibiogram and serological typing of Staphylococcus aureus isolates recovered from Al-Makased Hospital in East Jerusalem.

Staphylococcus aureus is a major cause of nosocomial infections and a risk in patients who have either undergone surgery or are on haemodialysis. The S. aureus infections in patients admitted to the clinical departments of Al-Makased Charitable Hospital in Jerusalem during a period of one year were investigated. Isolates included were from blood, surgical wounds, or other nonsuperficial sites. Of 63 isolates available for analysis, 46 (73.0%) expressed type 8 capsular polysaccharide; 13 (20.7%), type 5 capsular polysaccharide; only 4 isolates (6.3%) did not express type 5 or type 8 antibodies. The strains fitted in 7 different antibiogram types, with the type showing resistance only to penicillin and ampicillin prevalent in 34 out of 63 isolates (54.0%). Of the 12 methicillin-resistant S. aureus (MRSA) isolates (19.1%), 8(66.7%) possessed the type 8 capsule and 4(33.7%) the type 5 capsule. Pulsed-field gel electrophoresis of all isolates with the restriction-endonuclease enzymes Sma I revealed 34 patterns demonstrating that no single methicillin-sensitive S. aureus strain was endemic in the hospital. However, all MRSA isolates with a type 8 capsule showed identical PFGE patterns using the 2 restriction-endonuclease enzymes Sma I and SST II. Moreover, type 5 isolates showed identical patterns (one isolate differed from the rest with one band only). These data suggest and confirm the clonality of type 5 and type 8 MRSA isolates. Analysing the results of the capsular and antibiogram typing schemes in conjunction proved useful and suggested that such an analysis can be employed as a helpful epidemiological tool in hospitals with limited resources.

Relapses or reinfections: Analysis of a case of Clostridium difficile-associated colitis by two typing systems

Immunoblotting and pulsed-field gel electrophoresis of Clostridium difficile isolates were employed to differentiate reinfection by a newly acquired strain from relapse by an original strain in a 10-year-old patient with four episodes of C. difficile-associated colitis. Immunoblot typing demonstrated subserogroup K-1 of serogroup K for the first and second organisms, subserogroup A-1 of serogroup A for the third organism, and subserogroup G-4 of serogroup G for the fourth organism. PFGE analysis revealed consistent results with immunoblot analysis except that the strains from the fourth episode, whose DNA constantly degraded, were nontypable by this method. Five separate isolates of C. difficile from a specimen of each episode showed identical PFGE patterns, indicating that infections of multiple strains probably did not occur in this patient. These typing results suggested that the second episode after a 17-day course of vancomycin therapy represented a relapse by the strain causing the first episode, and that the third and fourth episodes after tapering vancomycin therapy were reinfections by other strains. Both immunoblot and PFGE typing systems are promising tools for analyzing recurrence of C. difficile infection.